1. The Field of the Invention
The invention relates to method of treating molluscum contagiosum warts.
2. The Relevant Technology
Molluscum contagiosum is a viral infection of the skin or occasionally of the mucous membranes, sometimes called water warts. It is caused by a DNA poxvirus called the molluscum contagiosum virus (MCV). MCV has no nonhuman-animal reservoir and infects only humans). There are four types of MCV, MCV-1 to -4; MCV-1 is the most prevalent and MCV-2 is seen usually in adults and often sexually transmitted. This common viral disease has a higher incidence in children, sexually active adults, and those who are immunodeficient. The infection is most common in children aged one to ten years old. MC can affect any area of the skin but is most common on the trunk of the body, arms, and legs. It is spread through direct contact or by shared items such as clothing or towels. Worldwide, Approximately 122 million people were affected by molluscum contagiosum as of 2010 (1.8% of the population).
The virus commonly spreads through skin-to-skin contact. This includes sexual contact or touching or scratching the bumps and then touching the skin. Handling objects that have the virus on them (fomites), such as a towel, can also result in infection. The virus can spread from one part of the body to another or to other people. The virus can be spread among children at day care or at school. Molluscum contagiosum is contagious until the bumps are gone (which, if untreated, may last up to 6 months or longer).
The time from infection to the appearance of lesions can range up to 6 months, with an average incubation period between 2 and 7 weeks. A person infect with Molluscum contagiosum can have one or many warts on one or more parts of the body. In some cases, dozens or even hundreds of unsightly warts can be seen up and down a person's arms and legs. Molluscum contagiosum lesions are flesh-colored, dome-shaped, and pearly in appearance. They are often 1 to 5 millimeters in diameter, with a dimpled center. They are generally not painful, but they may itch or become irritated. Picking or scratching the bumps may lead to further infection or scarring. In about 10% of the cases, eczema develops around the lesions. They may occasionally be complicated by secondary bacterial infections. In some cases the dimpled section may bleed.
The viral infection is limited to a localized area on the topmost layer of the epidermis. Once the virus-containing head of the lesion has been destroyed, the infection is gone. The central waxy core contains the virus. In a process called autoinoculation, the virus may spread to neighboring skin areas when the infected person touches the affected area and then touches an unaffected area. Children are particularly susceptible to autoinoculation, and may have widespread clusters of lesions.
Individual molluscum lesions may go away on their own and are reported as lasting generally from 6 weeks to 3 months. The lesions may propagate via autoinoculation so an outbreak generally lasts longer. Mean durations for an outbreak are variously reported from 8 months to about 18 months, but durations are reported as widely as 6 months to 5 years, lasting longer in immunosuppressed individuals.
Histologically, molluscum contagiosum is characterized by molluscume bodies in the epidermis above the stratum basale, which consist of large cells with abundant granular eosinophilic cytoplasm (accumulated virons) and a small peripheral nucleus.
Although treatment may sometimes be unnecessary, no single approach has been convincingly shown to be effective. It should also be noted that treatments which cause the skin on or near the lesions to rupture may spread the infection further, much like scratching does. In some cases, astringent chemicals can be applied to the surface of molluscum lesions to destroy successive layers of the skin. Examples include potassium hydrochloride, and cantharidin. For mild cases, over-the-counter wart medicines, such as salicylic acid may or may not shorten infection duration. Daily topical application of tretinoin cream may also trigger resolution. These treatments typically require several months for the infection to clear, and are often associated with intense inflammation and possibly discomfort. Given the slowness and ineffectiveness of such “treatments,” pediatricians and dermatologists often advise their clients that there is no known cure for molluscum contagiosum, although some have advised using tea tree oil to relieve symptoms, such as itching or burning.
Imiquimod has also been used with minimal success. Imiquimod is a form of immunotherapy. Immunotherapy triggers the immune system to fight the virus causing the skin growth. Imiquimod is applied 3 times per week, left on the skin for 6 to 10 hours, and washed off. A cure may take from 4 to 16 weeks. Small studies have indicated that it is successful about 80% of the time. Another dose regimen includes applying imiquimod three times daily for 5 consecutive days each week. Given the lengthiness of such treatments, they are largely ineffective unless the patient is highly motivated and very patient.
Surgical treatments include cryosurgery, in which liquid nitrogen is used to freeze and destroy lesions, as well as scraping them off with a curette. Application of liquid nitrogen may cause burning or stinging at the treated site, which may persist for a few minutes after the treatment. Scarring or loss of color can complicate both these treatments. With liquid nitrogen, a blister may form at the treatment site, but it will slough off in two to four weeks. Although its use is banned by the FDA in the United States in its pure, undiluted form, the topical blistering agent cantharidin can be effective. Although cryosurgery and curette scraping are relatively “painless” procedures, they can leave scars and/or permanent white (depigmented) marks.
Pulsed dye laser therapy may be used for cases that are persistent and do not resolve following other measures. As of 2009, however, there is no evidence that laser treatment is efficacious for genital lesions.
Most cases of molluscum contagiosum will clear up naturally within two years (usually within nine months). However, so long as the skin growths are present, there is a possibility of transmitting the infection to another person. When the growths are gone, the possibility for spreading the infection is ended.
Unlike herpes viruses, which can remain inactive in the body for months or years before reappearing, molluscum contagiosum does not remain in the body when the growths are gone from the skin and will not reappear on their own. However, there is no permanent immunity to the virus, and it is possible to become infected again upon exposure to an infected person.
If left untreated, molluscum growth can reach sizes as large as a pea or a marble. Spontaneous resolution of large lesions can occur, but will leave larger crater-like growth. As many treatment options are available, prognosis for minimal scarring is best if treatment is initiated while lesions are small.